1 - There are many markets out there, what i want to know is WHY is MtGox used as the "gold standard". What i mean is for example there are a few applications out there that give you rates. Why would i want to know what the rates are for MtGox and not the others. As a matter of fact why would someone in their right mind want to buy Bitcoins from MtGox where there are cheaper markets. I Guess my main question here is according to what i mention why would someone still buy from MtGox. Is there some piece of crucial info that i am missing here?

2 - From a trading point of view could someone possibly buy lets say $5000 worth of BitCoins at the lowest price lets say 18.0 and then sell it back in another market which has a sell price of 20.0. Just doing that you can gain much profits.

And if this is all possible. Isent it more profitable to trade from one market to another instead of purely mining?